The thermal performance of closed-cell foams as an insulation device depends on the thermal conductivity. In these systems, the heat transfer mode associated with the convective contribution is generally ignored, and studies are based on the thermo-physical properties that emerge from the conductive contribution, while others include a term for radiative transport. The criterion found in the literature for disregarding convective heat flux is the cell diameter; however, the cell size for which convection is effectively suppressed has not been clearly disclosed, and it is variously quoted in the range 3–10 mm. In practice, changes in thermal conductivity are also attributed to the convection heat transfer mode; hence, natural convection in porous materials is worthy of research. This work extends the field of study of conjugate heat transfer (convection and conduction) in cellular materials using microstructure-based finite element analysis. For air-based insulating materials, the criteria to consider natural convection ($Ra={10}^3$) is met by cavities with sizes of 9.06 mm; however, convection is developed into several cavities despite their sizes being lower than 9.06 mm, hence, the average pore size that can effectively suppress the convective heat transfer is 6.0 mm. The amount of heat transported by convection is about 20% of the heat transported by conduction within the foam in a $Ra={10}^3$, which, in turn, produces an increasing average of the conductivity of about 4.5%, with respect to a constant value.

Lead was recovered through a direct smelting reduction route from a lead concentrate by using mixtures of Na₂CO₃ and SiC to 1000 °C. The lead concentrate was obtained from the mining State of Zacatecas, México by traditional mineral processing and froth flotation. The experimental trials showed that 86 wt.% of lead with a purity up to 97% can be recovered from the lead concentrate by a single step reduction process when 40 wt.% Na₂CO₃ and 0.4 g SiC were used in the initial charge. The process was modeled in the thermodynamic software FactSage 7.3 to evaluate the effect of adding different amounts of Na₂CO₃ on the lead recovery rates while holding constant the SiC amount and temperature. The stability phase diagram obtained showed that an addition of 34 wt.% Na₂CO₃ was enough to reach the highest lead recovery. It was observed that the interaction of Na₂CO₃ and SiC at a high temperature promotes the formation of C and Na₂O, and SiO₂, respectively, where the Na₂O partially bonds with silica and sulfur forming Na₂S and sodium silicates which may decrease the SO₂ emissions and increase the weather degradation of the slag. The PbS was mainly reduced by the produced C and CO formed by the interaction between Na₂CO₃ and SiC at 1000 °C. The predicted results reasonably match with those obtained experimentally in the lead recovery rates and compounds formation.

Ductile iron (DI) can acquire various properties with the addition of alloying elements and through heat treatment. In this work, the effects of vanadium and molybdenum on the microstructure and corrosion resistance of DI and austempered ductile iron (ADI) were studied. Corrosion resistance was evaluated by potentiodynamic polarization techniques in 0.5 M H2SO4, 0.5 M NaCl, and 05 M NaOH as electrolyte. The ADI alloyed with vanadium presented anupper ausferritic microstructure consisting of broad ferrite needles, while the combination of vanadium and molybdenum allows obtaining a fine microstructure composed of ausferrite and thin needles of ferrite; this microstructure improves the corrosion resistance in NaCI and NaOH. The DI’s showed corrosion due to the galvanic pair between the graphite nodule and the ferrite; however, a high amount of carbide increases the corrosion resistance in H2SO4.

This paper presents a computational study on bottom gas injection in a cylindrical tank. The bubble formation at submerged orifices, bubble rising, and interactions between bubbles and bubbles with the free surface were studied using the conservative level set method (CLSM). Since the gas injection is an important technique in various fields and this process is quite complicated, the scenario was chosen to quantify the efficacy of the CLSM to describe the gas-liquid complex interactions with fast changes in the surface tension force and buoyancy force. The simulation accuracy is verified with the grid convergence index (GCI) approach and Richardson Extrapolation (RE) and is validated by comparing the numerical results with experimental observations, theoretical equations, and published data. The results show that the CLSM accurately reproduces the bubble formation frequency, and that it can handle complicated bubble shapes. Moreover, it captures the challenging phenomena of interaction between bubbles and free surface, the jet of liquid produced when bubbles break through the free surface, and the rupture of the film of liquid. Therefore, the CLSM is a robust numerical technique to describe gas-liquid complex interactions, and it is suited to simulate the gas injection operation.

This work is aimed to analyze the effect of concentration of Cu2+ and Pb2+ ions in flotation process water with Sphalerite activation, the analysis was performed at Cozamin Mining flotation circuit. This analysis demonstrates that (i) It is possible to determine the relationship between Sodium...

Powder addition onto a molten-lead surface followed by stirring is widely used for desilvering during lead bullion refining operations. We model submerged zinc particle injection by coupling (i) a transient particle–metal reaction following Ohguchi with a time-dependent reaction efficiency E, (ii) a Stefan-type estimate of the zinc melting time Tf, and (iii) hydrodynamic descriptors of residence (τ_res) and mixing (τ_mix) times. The model is validated against experiments under a benchmark condition (gas velocity U = 3.32 m/s, 70% submergence), achieving a mean absolute percentage error of 1.13% for the experimental desilvering curve. A parametric study over lance submergence (30–90% of bath depth), injection velocity (3.32–9.79 m/s), and geometric scalings of lance and kettle identifies conditions where the hydrodynamic residence time τres approaches the Stefan melting time, maximizing liquid-Zn contact with molten Pb. Specifically, the proposed optimum balances the competing effects of plume buoyancy at high velocities—which tends to reduce residence time—against the deeper injection depth, ensuring that particles remain submerged long enough to fully melt and react. Within 16 simulated scenarios, the pair “90% submergence + U = 9.79 m/s” provides the best multi-criteria performance (desilvering fraction, E, and residence time) under realistic constraints. A parametric sensitivity analysis ranks injection velocity and submergence as the dominant levers, with geometry playing a secondary role over the tested ranges. The coupled hydrodynamic–kinetic framework provides quantitative guidance for optimizing industrial desilvering by particle injection and is extensible to other powder-injection refining operations.